effect of hydrogen concentration on vented explosions
DESCRIPTION
Effect of Hydrogen Concentration on Vented Explosions. C. Regis Bauwens, Jenny Chao, Sergey B. Dorofeev 6 th ICHS Sept. 13 th , 2011. Outline. Background Explosion Phenomena Experiments Correlation Conclusion/Summary Questions. Background. Vented Explosions. Background. Motivation - PowerPoint PPT PresentationTRANSCRIPT
Effect of Hydrogen Concentration on
Vented Explosions
C. Regis Bauwens, Jenny Chao, Sergey B. Dorofeev
6th ICHSSept. 13th, 2011
Outline• Background• Explosion Phenomena• Experiments• Correlation• Conclusion/Summary• Questions
Background• Vented Explosions
Background• Motivation
– Necessary to properly size vents• Aim to minimize vent size while providing
adequate protection
– Existing empirical standards based on limited data• Predictions off by more than order of
magnitude• Greatly under predicts hydrogen-air
mixtures
Background• Vented Explosion Research Program
– Generate a set of experimental data on vented explosions varying:• mixture composition• ignition location• vent size• presence of obstacles • size of enclosure• vent deployment pressure/panel mass
– Develop engineering tools/CFD models
– Develop/improve vent size correlations
Background• Experimental Setup
• Volume: 64 m3
• Vent size: 5.4 m2
• 12 – 19 % vol. hydrogen-air
Background• Experimental Setup
– Instrumentation layout:
Background• Center ignition 19% hydrogen-air
Pext
Pvib
Explosion Phenomena• External Explosion
Background• Rayleigh-Taylor Instability
Explosion Phenomena• Flame-acoustic interactions
Explosion Phenomena• Lewis Number Effect
– LE < 1 enhances hydrodynamic flame instabilities
– LE decreases as hydrogen concentration decreases
– Increases effective burning velocity of flame
Experiments• Flame speed
Experiments• Flame speed
Normalized by σSL Normalized by σSLΞLE
19.0 LELE
Experiments• Internal Pressure
80 Hz Low Pass Filtered 80 Hz High Pass Filtered
Outline• Background• Explosion Phenomena• Experiments• Correlation• Conclusion/Summary• Questions
Correlation• Model Description
– Previous studies found each pressure peak independent of one another
– Pressure peaks occur when volume production matches volumetric flow rate through vent
• Rate of volume production depends on flame area, flame speed
• Rate of venting function of pressure across vent, vent size and density of vented gas
Correlation• Model Description
12
vcd
fu1
0
e
0
)1(211
Aa
ASpp
pp
burning velocity
maximum flame area
external explosion pressure
production of combustion products = loss of volume due to venting
Correlation• External Explosion Peak, Pext
0
0.1
0.2
0.3
0.4
0.5
0 0.1 0.2 0.3 0.4 0.5
Mod
eled
Pex
t(b
ar)
Measured Pext (bar)
Center IgnitionBack Ignition
0
0.1
0.2
0.3
0.4
0.5
0 0.1 0.2 0.3 0.4 0.5
Mod
eled
Pex
t(b
ar)
Measured Pext (bar)
Center IgnitionBack Ignition
19.0 LELE2LE
Correlation• Flame-Acoustic Peak, Pvib
0
0.05
0.1
0.15
0.2
0.25
0.3
0 0.05 0.1 0.15 0.2 0.25 0.3
Mod
eled
Pvi
b(b
ar)
Measured Pvib (bar)
Center IgnitionBack IgnitionFront Ignition
0
0.05
0.1
0.15
0.2
0.25
0.3
0 0.05 0.1 0.15 0.2 0.25 0.3
Mod
eled
Pvi
b(b
ar)
Measured Pvib (bar)
Center IgnitionBack IgnitionFront Ignition
19.0 LELE2LE
Discussion• Model accurately reproduces trends
for peak pressures
• Valid over wide range of initial conditions and ignition locations
• Only two empirical constants in model
Conclusion/Summary• Experiments
– Experiments performed for 12-19% vol. hydrogen-air mixtures
– Throughout range of concentrations same peaks present
– High frequency flame-acoustic interactions increase in amplitude with lower concentration
– Flame-acoustic interactions did not result in more damaging over-pressures
Conclusion/Summary• Correlation
– Previously developed model performs well across range of concentrations
– Adding LE correction slightly improves performance of model
– LE correction may have larger contribution at higher concentrations
Questions?